Xlvi . INTRODUCTION. 



of the contiguous cell in the next central layer; the angles at 

 which the elongated nuclei or successive portions of the dentinal 

 tubuli thus unite constitute the secondary gyrations or curves of 

 those cells. The primary curves depend upon the arrangement of 

 the primary linear series of the parent-cells. 



The original contour of these cells is most discernible after 

 calcification in the teeth of the Mammalian class, and here with 

 different degrees of distinctness in different species. They are 

 the true dentinal cells, and must not be confounded with the so 

 called ' intertubular or interfibrous cells', the first notice of which 

 is due to Retzius.(l) The diameter of the dentinal or calcified 



(1) The able Translator of "Miiller's Physiology," Part I, 2nd. Edit., p. 431, gives the fact 



that the substance between the tubuli of the ivory is composed of distinct cells, some of which 



contain smaller cells, on the authority of a " Report of the Meeting of the British Association," 



Athenaeum, No. 620, 1839. Retzius (" Mikroskopiska undersokningar ofver Tandemes, sardeles 



Tandbenets, struktur," 8vo. 1837, passim) describes the intertubular cells in the dentine of several 



of the animal's teeth which he examined. In the molar of the Hog, for example, he says : 



" short branches proceed from the sides of the main tubes throughout their whole extent, 



some of which terminate in dilated ends, like cells ;" and a little further on : " only a few opake 



cellules" (kalk celler) " were visible in the interspaces of the tubes," (pp. 33 & 34.) In the 



molar of a Rhinoceros, Retzius saw many of the lateral branches of the dentinal tubes 



terminating in large cells : — "These cells," he says, " were thinly arranged in the intertubular 



spaces," (af hvilka manga tydligen syntes sluta sig i stora kalk celler ; dessa lago glest kring 



spridda i stamrorens mellanrum) p. 32. M. Serres in his Report on certain Microscopic 



])ieparations, submitted by Mr. Nasmyth to the French Academy, in proof of his discovery of 



the intertubular cells, says of four sections from the teeth of the Megalichthys, Lamna, 



Cachalot, and Elk : — " Sur ces preparations et sous un grossissement de deux a quatre cents 



diametres on distingue entre les fibres dont I'ivoire se compose, des areoles nombreuses 



a parois distinctes." He verifies this as the " fait capital du travail de M. Nasmyth," and 



gives it the character of novelty by contrasting it with an alleged opinion of Retzius, whom 



M. Serres aflSrms to have regarded the intertubular tissue (tissue interfibreux) as amorphous! 



CComple Rendu de Seance de I'Acade'mie des Sciences,' 5 Decembre, 1842, p. 1055.) On 



what authority M. Serres cites me (loc. cit. pp. 1056 & 1057) as contending for the 



priority of the discovery of the intertubular, or interfibrous cells, I know not : he does not 



